Several improved synthetic pyrethroid pesticides have been developed in recent years and, for example, the following synthetic pyrethroid compounds described in the Proceedings of the Tenth Symposium on Agricultural Chemicals (published Sept. 15, 1977), in particular, are now being evaluated for their practical applicability because they have been found to have the advantages mentioned below.
______________________________________ ##STR5## Phenothrin [hereinafter referred to as Compound (A)] ##STR6## Permethrin [hereinafter referred to as Compound (B)] ##STR7## Cypermethrin [hereinafter referred to as Compound (C)] ##STR8## Decamethrin [hereinafter referred to as Compound (D)] ##STR9## Fenvalerate [hereinafter referred to as Compound (E)] ______________________________________
These compounds are characterized by:
(1) exceptionally high and fast-acting pesticidal effect; PA0 (2) a minimum of environmental residue which is a problem with organochlorine pesticides, whilst they have sufficiently high residual activity; PA0 (3) comparatively low toxicity to man and domestic animals; and PA0 (4) high pesticidal activity even against pests resistant to organophosphorus and/or carbamate pesticides.
Nonetheless, as pointed out in Kagaku-to-Seibutsu (Chemistry and Life) 14, 8 pages 549-556, natural pyrethrin and synthetic pyrethroid pesticides have very high toxicity to fish as compared with the organophosphorus, carbamate or chlorine-type pesticides thus far employed. This means that when such pyrethroid pesticides are applied to a paddy field for the control of agricultural pests, a water area for the control of aquatic pests such as the larvae of mosquitos, sand flies, etc. or a large tract of land including a lake, pond or river, for example by broadcasting from aircraft, these pesticides could destroy the fish inhabiting there. Certain pyrethroid pesticides less toxic to fish were described of late in German Offenlegungsschrift No. 2825197 and it is understood that these compounds represent some improvements in toxicity to fish. However, these pesticides are still by far more toxic to fish than the commonly used organophosphorus, carbamate and chlorine-type pesticides and are not satisfactory for use in the above-mentioned applications.
The intensive study undertaken by the present inventors with a view to developing a safe pesticidal compound which would possess all of the above-mentioned advantages of pyrethroid pesticides, (1) to (4), and, yet, be low in toxicity to fish has revealed that the substituted cyclopropanecarboxylic acid esters of the general formula (I) not only have the above-mentioned advantages (1) to (4) but, to our surprise, have a toxicity to fish which is only 1/5 to 1/1000 of the toxicity of the above pyrethroid pesticides known to have a reduced toxicity to fish and only 1/10 to 1/3000 of the toxicity of the above-mentioned synthetic pyrethroid compounds [i.e. Compounds (A), (B), (C), (D) and (E)]. It was also found that the substituted cyclopropanecarboxylic acid esters of general formula (I) each have a broadened pesticidal spectrum, displaying an unexpectedly high killing effect even on planthoppers to which many of the conventional pyrethroid pesticides are only very sparingly lethal, and do not cause any injury to crop plants. This invention is the culmination of the above findings.